1. Field of the Invention
The present invention relates generally to computer aided design (CAD) applications and geographic information systems (GIS), and in particular, to the creation and editing of interactive constraint-based alignment objects in a computer-implemented graphics system.
2. Description of the Related Art
Computer aided design (CAD) applications are traditionally used for creating and editing drawings (e.g., maps, floor plans, and engineering designs). Further, CAD applications enable users to create/modify highly precise and accurate drawings/maps. Civil engineers and surveyors, for whom precision and accuracy are of primary importance, have adopted CAD applications to speed data input and perform computations for design projects.
Geographic information systems (GIS) have been traditionally used for spatial analysis and mapping and allow users to store, retrieve, manipulate, analyze, and display geographically referenced data. However, traditional GIS have been aimed at general cartography and broad land-use analysis, and not precision design for the construction and management of real-world projects. In this regard, the geometric precision that many engineers require has not been provided by traditional GIS systems. Some GIS companies have attempted to use complex databases to model real-world objects. However, such databases are still built on points, lines, and polygons and cannot store geometric objects used in traditional CAD applications (e.g., true arcs or road spirals).
Many organizations have used both CAD and GIS tools in different departments to utilize the different specific features available. Further, data from original CAD drawings may be frequently imported or digitized for use in the GIS mapping environment. However, because of the limitations of GIS systems and/or CAD systems, during such a transition, data connectivity, accuracy, and geometric precision are often lost. Accordingly, what is needed is an integrated solution that provides the functionality and tools of a GIS system with the precision and accuracy of a CAD application.
In an attempt to address the above concerns, industry specific components were built on top of the CAD engine to address specialized needs and eventually, an integrated solution was developed (e.g., the AUTODESK LAND suite of software, including AUTOCAD, AUTODESK MAP, AUTODESK LAND DESKTOP and AUTODESK CIVIL DESIGN, all of which are available from the assignee of the present invention). Integrated solutions attempt to provide GIS functionality (e.g., multi-user editing, polygon overlay and analysis, topology, thematic mapping, etc.) within a CAD application and spatial database. The integrated solution allows civil engineers the ability to integrate the precision engineering tasks (from CAD) (e.g., site, roadway, and hydrological design) with the spatial analysis tools and data management of GIS. Such systems are known as CAD/GIS systems.
Nonetheless, the integrated solutions may have various limitations with regard to creating alignments between objects and then editing those alignments. In this regard, alignments are more of a “baseline” with which to reference design locations and lengths, for example, the centerline of a roadway in a CAD/GIS system.
What is needed in the art are improved techniques for creating and editing alignments between objects in CAD/GIS systems. The present invention satisfies those needs.